Conventionally, the optical waveguide is produced by irradiating a coating film of a liquid photosensitive monomer mixture with ultraviolet radiation via a mask (see PTL1). Although the resin (liquid photosensitive monomer mixture) has higher photo-curing sensitivity, the coating film of the resin has a higher surface tackiness. Therefore, the coating film is liable to be broken when being brought into contact with a roll in a continuous process such as a roll-to-roll process. Problematically, this results in poorer film productivity. For adaptability to the roll-to-roll process, a photosensitive resin which is solid at an ordinary temperature is generally used (see PTL2).
As the molecular weight of the so-called ordinary-temperature-solid photosensitive resin is increased, the flexibility of an uncured amorphous film of the photosensitive resin is increased, but the patterning resolution is disadvantageously reduced. As the molecular weight of the photosensitive resin is reduced, on the other hand, the patterning resolution is increased, but the flexibility is reduced. Problematically, there is a trade-off relationship between the flexibility and the patterning resolution of the ordinary-temperature-solid photosensitive resin.
An optical waveguide core layer material should satisfy requirements for various properties such as higher refractive index, higher transparency, higher patterning resolution and higher heat resistance. Therefore, optical waveguide makers give various considerations to combination and balance of ingredients to be blended to satisfy the property requirements. There is also a demand for a core layer material which is adaptable to the roll-to-roll process for mass production.
Where an attempt is made to satisfy the requirements for lower tackiness, flexibility and the like by providing an uncured film of the optical waveguide core layer material in the form of a dry film for the adaptability to the roll-to-roll process, the design flexibility is liable to be reduced in the development of the material. In addition, it is necessary to provide laminate bases on opposite surfaces of the uncured film to provide the dry film. For resource saving and cost saving, consideration is also given to the adaptability to a wet process in the development of the material (PTL3).